Chronology of Solar System Discovery

Prior to 1600

From the dawn of history until the beginning of the 17th century the known universe consisted of only 8 bodies:

    Earth
    Sun
    Moon
    Mercury
    Venus
    Mars
    Jupiter
    Saturn

plus the “fixed” stars. These are the ones that can be seen easily without any optical instruments. In Europe, the prevailing view was the Ptolemaic system with the Earth at the center and the other bodies revolving around it.

The 17th Century

In 1610 when Galileo first turned a telescope on the heavens and our knowledge of the universe exploded. By the end of the 17th century, 9 new bodies had been discovered and Copernicus’s heliocentric theory was widely accepted. The total number of known bodies had more than doubled to 17:

The 18th Century

Only 5 new bodies (not counting comets) were discovered in the 18th century (all by William Herschel) bringing the total to 22:

The 19th Century

The number of bodies in the solar system increased dramatically in the 19th century with the discovery of the asteroids (464 of which were known at by 1899) but only 9 more “major” bodies were discovered. The number of major bodies rose to 31 (almost double the 17th century total):

The Early 20th Century

In the first three quarters of the 20th century 13 more major bodies (and thousands of comets and asteroids) were discovered bringing the total up to 43:

The Space Age

27 more small moons were discovered by the two Voyager spacecraft:

The CCD Age

Dozens more small moons have been discovered in recent years with large ground based telescopes and CCD cameras. There are well over 100 now known; See JPL’s site for more details.